The present invention relates to a cooling structure for an integrated circuit to be used in an electronic device such as a data processor and, particularly, to a cooling structure in which an integrated circuit is cooled by circulating liquid coolant in the vicinity of the integrated circuit and absorbing heat generated by the integrated circuit by liquid coolant.
Examples of a conventional cooling structure for integrated circuit of this type are disclosed in "A Conduction-Cooled Module for High Performance LSI Devices" by S. Oktay and H. C. Kammerer, published in IBM J. RES. DEVELOP., Vol. 26, No. 1, Jan. 1982 and in Japanese Patent Application Disclosure No. Sho 60-160150.
The former example shows a first conventional structure in which a semi-spherical contact surface of a piston is pressed to a heat radiating surface of an integrated circuit formed on a wiring substrate by spring force to transmit heat generated in the integrated circuit through the piston, a gap filled with helium gas, a hat and an intermediate layer and, after heat is transmitted from the intermediate layer to a cooling plate, the latter is cooled by a coolant.
The latter example shows a second conventional cooling structure in which a heat conductive substrate, a deformable heat conductive member and a heat conductive plate are provided on a heat radiating surface of a chip on a printed circuit substrate and a thin-walled, elastically deformable bellow is provided on the heat conductive plate cooling is performed by jetting liquid coolant from a nozzle to the heat conductive plate within the bellow.
The cooling structure of the conventional integrated circuit which are disclosed in the above mentioned articles has defects which will be described below.
First, in the first conventional structure, the piston is always urged to the heat radiating surface of the integrated circuit by resilient force of the spring and therefore a load is exerted on a connecting portion between the integrated circuit and the wiring substrate, degrading reliability of the connecting portion.
Second, in the first conventional structure, in order to follow variations in height and tilting of the integrated circuit which may be caused when it is mounted on the wiring substrate, the contact surface of the piston with the integrated circuit is made spherical and a gap is provided between the hat and the piston.
As a result, an effective heat conducting area is reduced, resulting in degraded total cooling performance of the cooling structure.
Third, heat conduction coefficient obtainable in the first conventional structure is in the order of 0.1 to 0.5 [W/cm.sup.2 .degree. C.] since heat conduction is performed by forced convention of coolant in the coolant passage within the cooling plate. Therefore, the cooling capacity thereof may become insufficient when power consumption is increased with an increase of integration density of the integrated circuit.
Fourth, since, in the second conventional structure, the heat conducting substrate, the deformable heat conductor and the heat conducting plate are provided between the liquid coolant jetted from the nozzle and the chip which is the source of heat, it is very difficult to obtain high heat transmission, thus causing the cooling capability of the cooling structure to be low.